Method of preparing diphenyl acetic acid



United States Patent METHOD OF PREPAKINHC; DIPHENYL ACETIC C GeorgeKesslin, New York, N. Y., assignor to Kay-Fries Chemicals, Inc., WestHaverstraw, N. Y., a corporation of New York No Drawing. ApplicationOctober 10, 1951, Serial No. 250,814

6 Claims. (Cl. 260-515) This invention relates to an improved method ofpreparing pure diphenyl acetic acid in a single step process, givingunexpectedly high yields, and utilizing the lower aliphatic esters ofglyoxylic acid, such as the hemi-acetals and benzene as reagents, withchlorsulfonic acid and sulfuric acid as condensing agents.

In my prior application, Ser. No. 137,033, filed January 5, 1950, forMethod of Preparing Diphenyl Acetic Acid, now abandoned, I havedisclosed and claimed a novel process utilizing one mol of glyoxylicacid and two (2) mols of benzene, in an excess of benzene, withchlorsulfonic acid as a condensing agent. In the practice of thisprocess the yield of diphenyl acetic acid (93.2% pure) was 67.2% oftheory.

I have now found that by starting with a lower aliphatic ester, such asethyl glyoxylate hemi-acetal, the process can be carried out withunexpected results, viz., the diphenyl acetic acid is recovereddirectly, as a 100% pure product, requiring no recrystallization orother purifying steps, and the yield of the directly produced, pureproduct is very much greater than that of the crude (93.2% pure)diphenyl acetic acid produced according to my prior process, aboveidentified.

It is, therefore, among the features of novelty and advantage of thepresent invention to provide an improved process for the one-steppreparation of 100% pure diphenyl acetic acid.

It is also a feature of novelty and advantage of this invention toprovide such an improved process wherein the primary reagents comprisethe lower aliphatic esters of glyoxylic acid and benzene, withchlorsulfonic acid and sulfuric acid as condensing agents.

It is a further feature of novelty and advantage of this invention toprovide such an improved process wherein the primary reagents compriseethyl glyoxylatehemi-acetal and benzene, and the preferred condensingagent is chlorsulfonic acid.

The above and other desirable features of novelty and advantage of theinvention herein will be apparent from the accompanying specificationand claims, in which a preferred embodiment of the invention is setforth and claimed.

The lower aliphatic esters of glyoxylic acid comprehended herein are themethyl, ethyl, propyl, and butyl compounds, and their isomers.

The process herein is exemplified by the following run:

Materials 15.0 gms. ethyl glyoxylate-hemi-acetal 100.0 cc. benzene 58.3gms. chlorsulfonic acid 9.5 gms. NaOH in 300 cc. water 100.0 cc.methanol 25.0 gms. 96% HaSOe-made up to a solution.

Procedure The chlorsulfonic acid was added, with agitation, to

2,756,255 Patented July 24, 1956 ice the mixture of benzene and ester,over a one-hour period, at 20-30 C. This temperature was maintained forone hour longer, and then raised to 50 C., where it'was held for anotherhalf-hour. The total reaction time was 2% hours.

The resulting crude product, diphenyl acetic acid, is then purified inthe following manner:

The reaction mixture was quenched in approximately 600 cc. of coldwater, and the oily layer (top layer) was separated, then refluxed for 3hours with a mixture comprised of 9.5 gms. NaOH, 300 cc. water, and 100cc. methanol. The methanol was then distilled off at a vapor temperatureof C., and the distilland extracted with 50 cc. of toluene. The aqueouslayer formed was separated from the toluene layer and .blown free ofentrained toluene. The toluene-free aqueous liquor was decolorized bytreating with 0.5 gm. decolorizing carbon (NuChar) for one-half an hour,then filtered. The filtrate was acidified with the diluted (20%)sulfuric acid, until red to alkali test paper, and the precipitated purediphenyl acetic acid was filtered, dried, weighed and analyzed.

Results Weight of diphenyl acetic acid 16 gms. (analyzing pure bytitration). Melting point 145.9146.4 0. Theory 21.2 gms. Yield 74.4%.

NoTB.-A mixed melting point determination with a known sample of purediphenyl acetic acid showed no lowering of the melting point (M. P.146.1-146.9 C.).

It will now be appreciated that there has been provided an improvedprocess for the direct preparation of 100% pure diphenyl acetic acidfrom lower aliphatic esters of glyoxylic acid and benzene, using an acidcondensing agent.

What is claimed is:

l. The improved method of preparing diphenyl acetic acid comprisingreacting one mole of a lower aliphatic ester of glyoxylic acidhemi-acetal and two moles of benzene, in the presence of a condensingagent of the group consisting of chlorsulfonic acid and sulfuric acid.

2. The improved method of preparing diphenyl acetic acid comprisingreacting one mole of ethyl glyoxylate hemi-acetal and two moles ofbenzene in the presenc of chlorsulfonic acid as acondensing agent.

3. The improved method of preparing diphenyl acetic acid comprisingreacting one mole of ethyl glyoxylate hemi-acetal and two moles ofbenzene in the presence of sulfuric acid as a condensing agent.

4. The improved method of preparing diphenyl acetic acid comprisingreacting one mol of ethyl glyoxylate hemi-acetal and two mols ofbenzene, in an excess of benzene, and in the prmence of an acidcondensing agent of the group consisting of chlorsulfonic acid andsulfuric acid.

5. The improved method of preparing diphenyl acetic I acid comprisingpreparing a reaction bath comprised of reactive amounts of ethylglyoxylate hemi-acetal and benzene in an excess of benzene as a carrier,adding chlorsulfonic acid, as a condensing agent, to the reactionmixture over a one hour period, and at room temperature; maintaining thereaction at room temperature for another hour; then raising thetemperature of the reaction mixture to 50 C., and maintaining themixture at this temperature for one-half an hour.

6. The method of recovering diphenyl acetic acid from a reaction mixtureprepared according to the method of claim 5, comprising quenching thereaction mixture in cold ater, yvhereby toform an oily top layercontaining the diphenyl acetic acid ethyl ester and a bottom aqueouslayer; separating the layers; refluxing the oily layer with an alcoholicsolution of sodiunphydroxide; heating the refluxed mixture, anddistilling oft the ethanol at a vapor temperature of 9 5 "(3.;extracting thealcohol-free residue with toluene, whereby an aqueouslayer and a toluene layer are formed; blowing the aqueouslayer with airto remov the toluene therein, and, decolorizing' the toluene-freeresidue; acidifying the deeolor'ized residue to precipitate purediphenyl acetic acid; and filtering and drying the acid.

4 References Cited in the file of this patent UNITED STATES PATENTS2,517,856 Elkinton et a1 Aug. 8, 1950 OTHER REFERENCES Boettinger:Archiv. de Pharm., vol. 233, pp. 111-118 1895) Ostromisslenski: Ber.Deut. Chem, vol. 41, page 3029,

Vieles et al.: Bulletin Soc. Chim. de France, vol. 1947, pp. 24725 1.

1. THE IMPROVED METHOD OF PREPARING DIPHENYL ACETIC ACID COMPRISINGREACTING ONE MOLE OF A LOWER ALIPHATIC ESTER OF GLYOXYLIC ACIDHEMI-ACETAL AND TWO MOLES OF BENZENE, IN THE PRESENCE OF A CONDENSINGAGENT OF THE GROUP CONSISTING OF CHLORSULFONIC ACID AND SULFURIC ACID.